Electrical furnace.



N0.'75-9,9o9. v PATBNTED MAY 17, 1904,

R. ,M. PELTON. ELECTRICAL FURNACE.

APPLICATION PILBD'DEO. 3, 1902..

N0 MODEL. 7 I 2 SHEETS-SHEET 1.

aged-ATTORNEY vN0. 759,909. v PATENTED MAY 17, 1904.

R. M. PELTON.

ELECTRICAL FURNACE. APPLICATION FILED DBO. a, 1902.

H6 110mm.

2. SHEETS-SHEET 2.

9&4 ATTORNEY Patented May 17, 1904.

PATENT OFFICE.

RICHARD M. PELTON, OF DETROIT, MICHIGAN.

ELECTRICAL FURNACE.

SPECIFICATION forming part of Letters Patent No. 759,909, dated May 17, 1904.

Application filed'December 3, 1902. Serial No. 133,686. (No model.)

To all whom it may concern.-

Be it known that I, RICHARD M. PELToN, a citizen of the United States, and a resident of Detroit, in the county of Wayne and State of Michigan, have invented certain new and useful Improvements in Dentists Furnaces, of which the following is a specification.

- struction thereof, substantially as hereinafter described, and particularly pointed out in the subjoined claims. 7 In the drawings, Figure 1 is a central vertical longitudinal section of my improved dentists furnace. Fig. 2 is a perspective view of the core, around which is wound the electrical heating-wires. Fig. 3 is a similar view showing an outer covering of refractory material applied to the coils of wire after they have been wound around the core, parts thereof being broken away to show the concealed parts underneath. Fig. 4: is a central vertical section of the muflle as finished with its lining of refractory material underneath the coils of wire after the core has been removed. In the drawings, 5 5 5 are heating-wires, preferably made of platinum. They are first wound around a core or form 6, made of wood or any suitable material, which has been fashioned into the shape of the interior of the muffle. In the winding the coils are preferably placed relatively close together at a, where the open end of the muffle is to be, so as to compensate for the storage of heat at the middle and closed end of the muflie, slightly farther apart at I), where the closed end of the muflle is to be, and much wider apart at 0, where the middle portion of the muflie is to be, whereby the heat is uniformly distributed throughout the interior of the entire muflie and the danger of destruction of the heatingwires is avoided. After the wires 5 5 have been so wound and the coils so spaced they are covered while-still on theform 6 with an outer layer 7 of fire-clay or other refractory material. This is applied by mixing the'same with water. When it has dried, it serves to hold the coils in position and permits of the removal of the form 6. After such removal the surface inside of the wires is coated with an inner layer 8 of refractory material similar to that used for the layer 7, and the whole muffle 9 thus formed is dried and baked and is ready to be placed in its casing. It will be seen that the wires 5 5 are embedded between two layers of refractory material. It will be understood, of course, that the wires 5 are provided with free ends projecting through the walls of the muffle in order to connect them with the electrical conductors. The muffle 9 as thus made has a flat bottom and an arched top. It is then placed within a substantially cylindrical shell or casing 10, made of any suitable metal, the space between the shell and the mufiie being packed with wet asbestos 11 and a wall of refractory material 12 being placed over the rear end of the asbestos packing and baked there to keep it in place. The wires 5 project through the layer 11 and wall 12 and are attached to suitable binding-posts 13 in the rear of the shell. I

The whole furnace is supported upon a granite base 20. Secured to this by screws or in any suitable manner are two upright castings 21 21, each provided with fsuitable apertures to admit of access to tlijeinuflie or furnace proper and held together by'connecting rods 22, secured at their ends by screws 23. Ashell 24:, of sheet metal, fits into agroove 25 in each casting 21 and incloses the entire apparatus, thus keeping the heat in, preventing meddling with its parts, and forming a more sightly structure.

Inside of the shell 24; and between the two castings 21 21 are located the resistance-wires 30, which are suitably insulated and are so arranged that they surroundor encircle the muffle, whereby said muffle is placed within the rheostat, thus securing compactness and maximum efiiciency in respect of the retention of heat. In the construction herein shown these resistance-wires are arranged in coils 31 31, wound around ametal drum or barrel 32, and are suitably spaced and insulated from each other by means of asbestos packing The coils 31 31 terminate in wires 3a 34, which are in electrical connection with contact-points located on the granite base 20 and a switch-lever 35, which cuts them in or out of circuit in the usual manner. This is a very convenient construction.

At the rear of the apparatus are the wires 40, connecting with the heating wires 5 5 through the binding-posts 13.

In front of the open end of the muffle is a mica door 50, pivoted on a screw 51 or otherwise suitably secured in place. The front casting 21 is provided with a projecting flange or platform 52 in front of the mica door. The mica being transparent permits of the examination of the materials within the muffle and yet can readily be removed to open the muflie when it is desired to do so.

What I claim is 1. A dentists furnace comprising a muffle having a hollow shell of refractory material closed at one end by a non-wired wall and open at the other end, the said shell having heating-wires coiled continuously completely around it from its open end to the said nonwired wall, and arranged to distribute less lengths of resistance-coils per unit in length of the muffle in the middle portion of the furnace than at either end thereof and less at the closed end of the furnace than at the open end of the same, substantially as described.

2. A dentists furnace comprising a muffle having a hollow shell of refractory material closed at one end by a non-wired wall and open at the other end, the said shell having heatingwires completely embedded in it, coiled continuously completely around it from its open end to the said non-wired wall, and arranged to distribute less lengths of resistance-coils per unit in length of the muflie in the middle portion of the furnace than at either end thereof and less at the closed end of the furnace than at the open end of the same, substantially as described.

3. A dentists furnace, comprising amuffle of refractory material closed at one end by a fixed wall and at the other end by a removable wall, a metal drum or barrel surrounding the muffle, a plurality of resistance-wires arranged in coils around the same and insulated therefrom and means for cutting the same in and out of circuit with an energizing-conductor.

4:. A dentists furnace, comprising a mufiie of refractory material closed at one end by a fixed wall and at the other end by a removable wall, a surrounding layer of material which is a non-conductor of heat, a metal drum or barrel surrounding the muffle, a plurality of resistance-wires arranged in coils around the same and insulated therefrom and means for cutting the same in and out of circuit with an energizing-conductor.

5. A dentists furnace, comprising a muffle of refractory material closed at one end by a fixed wall and at the other end by a removable wall, a metal drum or barrel surrounding the muffle and a plurality of resistance-wires arranged in coils around the same and suitably spaced and insulated from each other by a heat-non-conducting material, and means for cutting the same in and out of circuit with an energizing-conductor.

6. A dentists furnace comprising a mu ffle of refractory material closed at one end by a fixed wall and at the other end by a removable wall, a metal drum or barrel surrounding the muffle, a plurality of insulated resistancewires arranged in coils around the same, terminal wires connected to said coils and in electrical connection with contact-points outside of the apparatus and means for cutting the same in and out of circuit with an energizingconductor.

7. A dentists furnace, comprising a muffle of. refractory material closed at one end by a fixed wall and at the other end by a removable wall, a surrounding layer of material which is a non-conductor of heat, a metal drum or barrel surrounding the muffle, a plurality of insulated resistance-wires arranged in coils around the same, terminal wires connected to said coils and in electrical connection with contact-points outside of the apparatus and means for cutting the same in and out of circuit with an energizing-conductor.

8. A dentists furnace, comprisinga muffle of refractory material closed at one end by a fixed wall and at the other end by a removable wall, a metal drum or barrel surrounding the muffle and a plurality of resistance-wires arranged in coils around the same and insulated therefrom, terminal wires connected to said coils and in electrical connection with contactpoints outside of the apparatus, and means for cutting the same in and out of circuit with an energizing-00nductor.

9. A dentists furnace comprising a mufiie of refractory material closed at one end by a fixed wall and at the other end by a movable wall, a metal drumor barrel surrounding the muffle, a plurality of resistance-wires arranged in coils around the same and insulated therefrom, a shell or case inclosing the parts enumerated, and means for cutting the resistance-wires in and out of circuit with an energizing-conductor.

10. A dentists furnace, comprising a muffle of refractory material closed at one end by a fixed wall and at the other end by a removable wall, a surrounding layer of material non-conductive of heat, a metal drum or barrel surrounding the muffle, a plurality of resistancewires arranged in coils around the same and insulated therefrom, a shell or case inclosing the parts enumeratedand means for cutting IIS the resistance-wires in and out of circuit with an energizing-conductor.

11. A dentists furnace, comprising a muflie of refractory material closed at one end by a fixed Wall and at the other end by a removable wall, a surrounding layer of material non-conductive of heat, a metal drum or barrel surrounding the muffle, a plurality of resistancewires arranged in coils around the same, and suitably spaced and insulated from each other by a heat-non-conducting material, a shell or case inclosing the parts enumerated and means for cutting the resistance-wires in and out of circuit with an energizing-conductor.

12. A dentists furnace comprising a muffle of refractory material closed at one end by a fixed wall and at the other end by a removable wall, a metal drum or barrel surrounding the muffle, a plurality of resistance-wires arranged in coils around the same and insulated therefrom, a shell or case inclosing the parts enumerated, terminal wires connected to said coils and in electrical connection with contactpoints outside of the inclosing shelland means for cutting the same in and out of circuit with an energizing-conductor.

13. An electrical furnace comprising amuffle provided with heating-Wires, and a rheostat comprising resistance-wires suitably insulated and encircling said muflie.

14. An electrical furnace comprisingamuffle provided with heating-coils, a rheostat h aving resistance-wires suitably insulated and encircling said muflle and a casing inclosing said rheostat.

15. An electrical furnace comprising a muffle provided with heating-wires, a casing for said muffie, a barrel encircling said casing, suitably insulated resistance wires extending around and supported by said barrel, and means for cutting said wires into and out of circuit.

16. An electrical furnace comprising a muffle provided with heating-wires, a casing for said muffle, comprising insulating material surrounding said muffle, a barrel surrounding said casing and arranged out of contact therewith, a'rheostat comprising suitably-insulated wires supported by and extending around said barrel, and an exterior casing inclosing said muffle, barrel and rheostat and having means for giving access to said muffle.

Witness my hand this 26th day of November, 1902, at the city of Detroit, in the county of Wayne and State of Michigan.

RICHARD M. PELTON.

Witnesses:

WM. L. JANUARY, TERRESSIA M. HOWARD. 

